Photosynthesis is a process by which biological entities utilize sunlight and CO2 to produce sugars for energy. Existing photoautotrophic organisms (i.e., plants, algae, and photosynthetic bacteria) are poorly suited for industrial bioprocessing. In particular, most organisms have slow doubling times (10-72 hrs) compared to industrialized heterotrophic organisms such as Escherichia coli (20 minutes). Additionally, photoautotrophic organisms are often susceptible to moderate variations in common environmental stresses including pH, temperature and salt tolerance. Such susceptibilities make industrial applications of photoautotrophs inefficient. Moreover, increasingly toxic environmental factors (for example, toxic pollutants including heavy metals, nitrogen and sulfer based industrial by-products) can further limit applications of photoautotrophs to particular industrial uses.
Desirable products which can potentially be produced in microorganisms (for example ethanol and other branched chain higher alcohols produced in engineered E. coli (Atsumi, et al. Nature (2008) vol 451:86-90)) have been found difficult to process in photoautotrophs because of incompatible or inefficient metabolic pathways of production or the complete absence of necessary cell based biocatalysts.
Thus, there is need in the art for improved photoautotrophic organisms that are better suited for industrial bioprocessing.